Yes, your voice can get stronger as you keep using the singing muscles. The more you use a muscle properly the stronger it gets. But if you keep singing and straining, it will break down your voice. Just like any other muscle usage you have to have correct form. You can still build muscle strength by singing more if you aren’t straining your muscles, but it won’t be as much as you could have if you were doing it with guidance from an experienced coach who can show you proper technique.